1. Field of the Invention
This invention relates to systems for assessing the quality of gemstones such as diamonds, and more particularly to a system and method for grading the cut of a diamond wherein a numerical score indicative of such overall cut quality is calculated for the stone.
2. Preliminary Discussion
Usually, layman diamond purchasers are informed that the cost and value of a diamond is based on the “4 C's”—Clarity, Colour, Cut (proportion), and Carat Weight. The higher grade a diamond receives in each of such categories, the better its overall quality and generally the more costly it will be. Layman diamond purchasers are usually not sufficiently skilled to effectively judge the quality of the cut a diamond. In addition, such quality may be judged differently by different persons despite their experience. Therefore, such purchasing decision is usually based largely upon the carat weight of the diamond, as well as on a visual inspection with the naked eye. Visual inspection is somewhat useful in judging the overall clarity and brilliance of a diamond, although less so to the untrained eye. However, while clarity affects the visual appearance of a diamond, the brilliance of a diamond is primarily but not entirely, influenced by the quality of the cut and proportions of the diamond.
Higher quality diamonds are usually accompanied by an independent grading report or certificate. Grading reports do not include appraisals indicative of the value or worth of a diamond, but rather give an independent expert opinion of the quality of a loose or unset stone. Independent grading reports are available from numerous organizations or labs, the most recognized of which are probably the Gemological Institute of America (GIA) and American Gem Society (AGS), and European Gem Lab (EGL).
The American Gem Society (AGS) certifies professional jewelers as Registered Jewelers (RJ), Certified Gemologists (CG), and Certified Gemologist Appraisers (CGA). In addition, the Grading Reports issued by AGS assigns 0–10 grades to the cut of round diamonds, with 0 being an ideal cut, 1 an excellent cut, 2 a very good cut, 3–4 a good cut, 5–7 a fair cut, and 8–10 a poor cut. Colour and clarity are also rated in a similar manner. The Gemological Institute of America (GIA) also has a scale for rating diamonds that is divided into two categories: colour and clarity. The GIA colour scale grades diamond from D (a total absence of colour) to Z (very deeply coloured). Clarity refers to the number of inclusions (internal marks) and blemishes (external marks) a diamond may have and how visible such marks are. Clarity is graded on a GIA clarity scale which ranges from Fl (flawless) to I-3 (very obvious and potentially damaging marks). GIA's proprietary grading system is well respected and generally considered on par with AGS's scale for color and clarity ratings. However, GIA does not grade cut, so merchants will send stones to AGS for cut scores, particularly if they are confident that the stone will get an AGS 0 or 1 cut score. One drawback of such grading systems is that they do not always consider the inter-relationships between the overall proportions of a diamond, which can significantly effect its appearance. For example, by varying the crown and pavilion angles and table percentage, brilliant diamonds not having “ideal” proportions may result. Research into the interrelationship of factors that contribute to the brilliance of a diamond is continuing.
Other gemological laboratories, such as Harold Weinstein Ltd. (HWL), have developed their own simple cut grading systems. In the HWL system, a stone having ideal proportions is considered an excellent cut and given an HW Grade of 1 to 1+, a good cut stone is given an HW Grade 2 to 3, an average cut is given an HW Grade 4, a commercial cut an HW Grade 5 to 6, and an irregular cut an HW Grade 7 to 8. Other laboratories such as the International Gemological Institute (IGI), Belgium High Diamond Council (HRD), Accredited Gem Appraiser (AGA) and European Gemological Laboratory (EGL) use either similar or individual systems for rating diamonds including the cut of such diamonds.
One drawback of having individual systems for all of such laboratories is that there is not an accepted industry wide standard for cut grading. This encourages dealers to “shop around” to get the most favorable grade or score for a diamond. Dealers are aware of which systems are more liberal with respect to some qualities than others, and therefore will send their stones to such companies depending upon what results they want or need to increase the perceived value of a stone. For example, some reports may have tight grading in the upper qualities but become more liberal as color falls. Another company is known for having well-graded high-grade stones, but for being quite liberal below F grade. Thus, borderline stones are usually sent to “softer” laboratories where dealers are reasonably sure they will receive a more favorable grade or score.
Thus, while there are various systems for individually judging the cut of a brilliant cut diamond, the fact that each laboratory has its own cut grading scale is confusing and leads to inexactness in the marketplace. In addition, none of such known scales is exact enough to be capable of distinguishing between minute differences between stones having closely similar cuts, so that stones having overall significantly different measurements and proportions may be accorded the same basic grade. It is also virtually impossible to accurately and objectively compare the quality of the cut of stones graded by different laboratories. In addition, lower quality stones currently are not typically provided with a grading report, so that many of such stones have less fungability and value than they would if they had a grading report.
3. Description of Related Art
Various devices and arrangements are found in the patented prior art for analyzing crystals and gemstones such as diamonds, although there is little prior art with respect to actual rating or scoring systems for the cut of a diamond. The following references are illustrative of such prior art.
U.S. Pat. No. 1,799,604 issued to F. F. Read entitled “Method and Apparatus for Identifying Crystals” discloses a system wherein a light source is shown upon a diamond, which fragments the light into a plurality of secondary rays. The angles of deflection of the secondary rays are then measured to determine the surface angles of the diamond. Such invention helps identify and distinguish between diamonds that would be considered virtually identical using older identification techniques, but in comparison to today's electronic measurement machines provides only a limited amount of information about the diamonds. In addition, the angles measured are not applied to a grading scale similar to the present inventor's grading system.
U.S. Pat. No. 4,125,770 issued to A. R. Lang entitled “Diamond Identification” teaches a technique for identifying gem quality diamonds in both a rough as well as a cut state wherein the topographical characteristics and internal defects of the stone that are not changed during cutting are analyzed using x-ray topography to measure x-ray diffraction at the “Bragg angle.” Lang does not attempt to grade or score the quality of the cut of a diamond, however.
U.S. Pat. No. 4,259,011 issued to J. C. Crumm et al. entitled “Optical Gem Analyzer” discloses an optical gem analyzing machine wherein the gem is irradiated with wide spectrum light and measurements are taken of the reflection and refraction angles of the light passing through the gem. The resulting measurements are then compared with known reference readings, and the quality of the cut is estimated based on the amount of deviation from such reference readings. No system or method applying such measured results to an overall numerical scale as in the present inventor's system is shown, however.
U.S. Pat. No. 4,291,975 issued to P. M. Raccah entitled “Apparatus for Determining the Color Characteristics of a Gem” discloses a device for measuring the color characteristics of a gem whereby the spectral distribution of light passed through the stone is measured and then compared against and graded using the Gemological Institute of America (GIA) color standard. Raccah teaches an apparatus for measuring gem color, rather than cut, and does not teach a new system for grading or rating either the color or cut quality of a diamond.
U.S. Pat. No. 4,482,245 issued to H. Makabe et al. entitled “Apparatus for Measuring the Color of a Brilliant-Cut Diamond,” discloses another apparatus for measuring the color of a diamond using a monochromator to analyze the spectrum of light passed through the diamond. The color measurements are then compared with standard GIA or International Confederation of Jewelry, Silverware, Diamonds, Pearls and Stones (C.I.B.J.O.) measurements to determine a color grade. Therefore, Makabke et al. does not teach a new grading system but rather another apparatus for analyzing a gem. Numerous other color measuring devices are known in the prior art.
U.S. Pat. No. 4,875,771 issued to H. J. Bowley entitled “Method for Assessing Diamond Quality” discloses a method wherein a laser Raman spectrometer calibrated to known diamond characteristics is used to determine the qualities of a diamond. Essentially a laser beam is directed at the diamond, and the intensity of the resulting scattered Raman radiation spectrum is compared with standard intensities. U.S. Pat. No. 4,900,147 also issued to H. J. Bowley entitled “Diamond Mapping” discloses a similar method wherein the intensity of Raman radiation is used to map the crystalline structure of a diamond. In addition, U.S. Pat. No. 4,907,875 also issued to H. J. Bowley et al. entitled “Diamond Separation Process,” discloses a diamond color assessment apparatus which measures Raman radiation wavelengths. A simple color rating system based on measured Raman wavelengths is disclosed in this reference; however, none of the Bowley et al. references teaches a grading scale similar to that of the present inventor used to rate the quality of the cut of a brilliant cut diamond.
U.S. Pat. No. 5,424,803 issued to D. Andrechuk entitled “Method and Apparatus for Determining the Facet Angles of a Gemstone,” discloses an apparatus that measures the angle of light reflected off of each facet of a gemstone when compared to a scale having angular measurement indicia thereon. Such information is indicative of the quality of a stone, particularly a diamond; however, Andrechuk does not teach a system for taking such information and using it to assign a quality grade or score to the stone, which is the basic method of the present invention.
U.S. Pat. No. 5,615,005 issued to K. A. Valente et al. entitled “Gemstone Evaluation System,” discloses an apparatus for evaluating primarily the color quality of gemstones using optical evaluation techniques. The gemstone is placed in a spherical analysis chamber and the wavelengths of light are passed through the gem and measured. Such information is digitized so that a computer program can compare the readings with standard readings for each pixel of data, and then for the gemstone as a whole. Images of such stones may also be taken and provided to prospective buyers, thereby decreasing the likelihood of return of the stone after actual inspection by such prospective buyer.
U.S. Pat. No. 5,950,178 issued to S. Borgato entitled “Data Processing System and Method for Facilitating Transactions in Diamonds” discloses a system for bringing together buyers and sellers of diamonds and facilitating diamonds sales between such parties. To facilitate such transactions, information concerning the quality and characteristics of diamonds is input into a computer system and displayed to prospective buyers and sellers. The diamonds may be categorized by weight class, cut depending upon the shape, or other parameters. Borgato does not teach a system for grading the overall quality of the cut of a brilliant cut diamond, however.
U.S. Pat. No. 5,966,673 issued to P. T. Shannon, Sr. entitled “System and Method for Computerized Evaluation of Gemstones” discloses a system for grading the cut of a gemstone wherein a three-dimensional profile of the stone is generated, rather than a two-dimensional model as with the two-dimensional profile of the standard Tolkowsky cut. The basic steps in the Shannon, Sr. method are building a data model of the gemstone, illuminating the stone with an illumination model, tracing the propagation of light within and exiting the stone, determining the light exiting the stone, and grading the stone based on such exiting light. Shannon, Sr. is directly primarily directed to a new cut analysis and measuring technique and machine, rather than a new cut grading system. However, such reference states that the grade may be an average, weighted sum, or other expression, and is a composite cut grade.
U.S. Pat. No. 6,020,954 issued to L. K. Aggarwal entitled “Method and Associated Apparatus for the Standardized Grading of Gemstones” discloses a method wherein a comprehensive analysis of the color, cut, clarity and other qualities of a gemstone is provided via a charge coupled device (CCD) camera, thereby claiming to provide more consistency between grading measurements. While the Aggarwal measuring and grading apparatus is one of the more comprehensive systems for analyzing a gemstone in the prior art, it still does not disclose a new or different rating system for generating a comprehensive single numerical score that may be used to evaluate or compare the quality of such diamonds.
Significant advances in the tools used to measure the accuracy of the cut and proportions of a diamond have been made in recent years. Although diamonds used to be graded for cut mostly by visual estimation, today there are several electronic machines available that analyze and determine the angles and proportion of the cuts. The most popular of these machines are manufactured by Sarin Technologies, Ltd. of Israel and having a U.S. office in New York, N.Y. The Sarin DiaScan and DiaMension machines are capable of more precisely measuring the facet angles and proportions of a cut diamond. The American Gem Society (AGS) uses the Sarin DiaScan machine to measure the proportions of diamonds in producing a grading report as well as in establishing its ideal cut standard. The DiaScan machine essentially measures facet inclinations by plotting interceptions using computerized machine vision and advanced 3D image processing, and provides consistently repeatable proportion measurements of round and fancy gemstones based on proportion measurements of international laboratories to an accuracy of ±0.2 degrees. Reports with such measurements are then generated and available for analysis. With the advent of such electronic measuring devices, which have now become standard in the industry, there is a need for a standardized grading diamond cut grading system that is accurate and objective and which assigns an overall cut quality grade or score to a diamond that is indicative of the quality of cut of such diamond and which is capable of distinguishing between minute differences in the cut of two stones. The present inventor with his cut grading system and method fulfills such need.